Single cells are the building blocks upon which complex tissue and systems are developed. It is believed that a detailed molecular fingerprint of individual cells in the context of the other cells within the system would provide a blueprint for manipulation of the system in an effort to produce predictable outcomes. For example assessment of individual hippocampal neurons in context of the various interacting cells from normal and Alzheimer's brain promises to highlight systemic constraints and influences on cell functioning in the disease state.
It has been possible to isolate and analyze the mRNA complement from individual cells for several years, in particular with regard to dispersed cells in culture. This information is intriguing but lacks the “systemic” regulation component associated with the cell being in intact live tissue. The isolation of single cells from in vivo is compromised by the complex structure of intact tissues with many types of cells tightly intermingled with one another. A number of techniques, including in situ transcription, automated fluorescent cell sorting (FACS-array) and laser capture microdissection (LCM), have to date attempted to generate gene expression information from single cells or populations of cell in situ. However, their use is limited the investigation of RNA in vivo in combination with other in vivo techniques, such as live-imaging or electrophysiology, a combination that would provide reforming and novel insights into in vivo functioning.
There is a need in the art for a method to quantify gene expression in individual live cells from an intact functioning tissue or organism. The present invention satisfies this need.